Recent improvements in this field have led to the development of transducers with piezoelectric membranes which deflect under an applied voltage or generate a potential difference upon being mechanically deformed. The membrane may be supported in the transducer housing by a yieldable mounting designed to keep it as free as possible from extraneous stresses, as with the aid of a resilient clamping ring. The housing itself, which must accommodate not only the membrane but also the associated electrodes, conductors and terminals, is usually split into a main body and a protective cover having apertures for the passage of the sound waves. The airspace surrounding the membrane within the housing, forming what may be described as a sound chamber, must conform closely to its design dimensions for optimum performance; this limits the tolerances within which the distances between confronting internal surfaces of the membrane-supporting body and the cover may vary.
Conventional constructions, in which the supporting body is encapsulated between two metallic shells constituting a cover and a base, create problems of access to the internal conductors after assembly if the two shells are permanently joined by welding. If they are separably interconnected by an edge bead, the maintenance of dimensional stability is difficult.